The Final World for Multisig Signing

Website · Research

---

What is Safe OpenSig?

Safe OpenSig is a mobile app for Safe multisig signers. It eliminates blind signing by showing you exactly what a transaction will do before you sign it on your hardware wallet.

The problem: When signing Safe transactions, you're often trusting a web interface to show you the truth. But browser extensions, phishing sites, or compromised frontends can manipulate what you see.

The solution: Safe OpenSig reconstructs the transaction locally on your device, simulates it, and shows you the real outcome: balance changes, permission changes, everything. Then you verify that what you're signing on your Ledger matches what you just verified.

Features

• Transaction Simulation: See exactly what will happen before signing: token transfers, balance changes, and permission modifications
• Ledger Hardware Wallet Support: Visual preview of what your Ledger Nano S/S+ will display, so you can verify character-by-character
• Multi-Chain Support: Works with Ethereum, Polygon, Optimism, Base, Arbitrum, Gnosis, and 10+ other networks
• Local Simulation: Transaction decoding and EVM execution happen entirely on your device, with state fetched from RPC nodes
• Trust-Minimized Verification: State is verified using Merkle proofs from multiple independent nodes

How It Works

1. Import or paste your Safe transaction data
2. Simulate the transaction locally using an embedded EVM
3. Review the decoded results: balance changes, approvals, and state modifications
4. Verify hashes match between the simulation and your hardware wallet
5. Sign with confidence knowing exactly what you're approving

Privacy & Analytics

Safe OpenSig is privacy-first. Analytics are opt-in and off by default. When enabled, the app sends a small set of anonymous behavioural events, no wallet addresses, no transaction hashes, no calldata, no amounts, no RPC URLs. Every event is documented in docs/analytics.md. You can self-host the analytics backend; see that doc. To build without analytics entirely, leave APTABASE_APP_KEY blank in your .env.

Getting Started

Prerequisites

• FVM (Flutter Version Management)
• Flutter 3.32.4 (managed by FVM)

Installation

# Clone the repository
git clone https://github.com/candidelabs/safe-opensig.git
cd safe-opensig

# Install dependencies
fvm flutter pub get

# Create .env file with RPC endpoints (see .env.example)

# Run the app
fvm flutter run

Environment Setup

Create a .env file with RPC node URLs for the networks you want to support. The app uses multiple nodes per network for trust-minimized state verification.

Architecture

Safe OpenSig operates on a three-pillar verification model:

Pillar	Description
Local REVM Simulation	Runs a Rust EVM directly on-device to decode transaction logic and preview state changes
Cryptographic Verification	Validates blockchain state using Merkle Patricia Trie proofs (eth_getProof) from multiple independent nodes
Hardware Emulation	Provides a 1:1 preview of Ledger screens for character-by-character verification before signing

For technical details on the trust-minimized verification approach, see our research post on ethresear.ch.

Tech Stack

• Framework: Flutter 3.32.4 (cross-platform mobile)
• State Management: Riverpod
• Storage: Hive (local-first, no cloud sync)
• EVM: REVM via Rust FFI
• Navigation: GoRouter

Project Structure

lib/
├── core/                            # Core infrastructure
│   ├── router/                      # Navigation and routing
│   ├── storage/                     # Local persistence
│   └── theme/                       # App theming
├── features/                        # Feature modules
│   ├── account_management/          # Safe account operations
│   ├── onboarding/                  # First-run experience
│   └── verify_safe_transaction/     # Transaction verification flow
├── shared/                          # Shared utilities
│   ├── models/                      # Domain models
│   ├── widgets/                     # Reusable UI components
│   └── services/                    # Business logic
└── main.dart

Contributing

We welcome contributions! Please follow these guidelines:

Development Workflow

1. Fork the repository
2. Create a feature branch from develop: git checkout -b feature/your-feature
3. Make your changes
4. Run fvm dart format . and fvm flutter analyze
5. Submit a pull request to develop

Branching Strategy

Branch	Purpose
main	Production releases
develop	Integration branch for PRs
feature/*	New features
fix/*	Bug fixes
hotfix/*	Critical production fixes

Security

Safe OpenSig is designed with security as the primary concern:

• Minimal network requests: Only connects to RPC nodes for state verification
• No external dependencies for transaction decoding
• Open source for full auditability

If you discover a security vulnerability, please report it responsibly.

Links

• Website
• Trust-Minimized Verification Research